Prior investigations have shown that the orbits of the giant
planets can migrate while they are still embedded in a
remnant disk of planetesimal debris (Fernandez and Ip 1984).
This hypothesis is further motivated by the highly eccentric
and inclined orbits of Pluto and its cohort of Kuiper Belt
objects that lie at Neptune's mean-motion resonances. One
natural explanation for the origin of these peculiar orbits
is that these bodies were captured by Neptune's sweeping
resonances as the planet's orbit expanded radially outwards
(Malhotra 1993, 1995).

We have investigated the planet-migration phenomenon via
direct numerical integration of a system of giant planets
embedded in a massive planetesimal debris disk. We find that
the rate and radial extent \Delta a of planet-migration
varies with the disk mass Md. Although most of the debris
disk is ultimately ejected by the giant planets, a small
fraction of the disk gets emplaced in the Oort Cloud. These
models also indicate that once the giant planets have
stirred up the planetesimal disk, the terrestrial zone of
the solar system suffers a period of considerable
bombardment. Estimates of how all these phenomena (e.g.,
planet-migration \Delta a, the development of the Oort
cloud, and impacts in the terrestrial zone) scale with the
disk mass Md shall be presented at conference time.
Comparison of model results to observations of the present
Kuiper Belt promise to yield an estimation for the disk mass
Md during the epoch of planet-migration.

The author(s) of this abstract have provided an email address
for comments about the abstract: hahn@lpi.jsc.nasa.gov